Bendix Commercial Vehicle Systems BA-921 COMPRESSOR_STD/CLOSED ROOM - Manual

DESCRIPTION
The function of the air compressor is to provide and maintain
air under pressure to operate devices in air brake systems.
The Bendix
® BA-921 ® compressor is a single-cylinder
reciprocating compressor with a rated displacement of
15.8 cubic feet per minute at 1250 RPM.
The compressor consists of a water-cooled cylinder
head assembly and an integral air-cooled crankcase
assembly.
The cylinder head assembly is made up of the cylinder
head, cooling plate and valve plate assembly and uses
two sealing gaskets. Depending on the application, the
cylinder head and cooling plate may be aluminum or cast
iron. The cylinder head contains air and water ports as
well as an unloader assembly. A cooling plate is located
between the cylinder head and valve plate assemblies and
assists in cooling.
The valve plate assembly consists of brazed steel plates
which have valve openings and passages for air and
engine coolant to fl ow into and out of the cylinder head.
SD-01-690
BENDIX ® BA-921 ® COMPRESSOR: STANDARD AND CLOSED ROOM
FIGURE 2 - BENDIX ® BA-921 ® COMPRESSOR: STANDARD AND CLOSED ROOM VERSIONS
FIGURE 1 - BENDIX ® BA-921 ® COMPRESSOR
Safety
Valve
Valve Plate
Assembly
Crankcase
Cylinder
Head
Cooling
Plate
Standard:
Aluminum
Cylinder Head
With 4
Bolts Standard:
Cast Iron
Cylinder Head
With 4
Bolts Closed Room:
Aluminum
Cylinder Head
With 6
Bolts
"STANDARD" AND "CLOSED ROOM" VERSIONS
This service data sheet covers two versions of the Bendix ® BA-921 ®
compressor. The fi rst version was originally released in 2002 and will
be referred to as the “Standard” compressor in this Service Data sheet.
The Standard compressor was offered on Caterpillar ACERT Medium
and Heavy duty engines, and the DDC S60 EGR (2002-06) engine.
These installations required an externally-mounted inlet check valve
(ICV) on the air inlet side of the compressor. Depending on whether the
air induction system was naturally aspirated or turbocharged dictated
whether or not additional hardware was required along with the ICV
(See Figure 6, page 3 and Section 1 of "Air Induction", on page 6).
The second version was originally released in 2007 and will be referred
to as the “Closed Room” compressor in this service data sheet.
This compressor is only permitted to be naturally aspirated – use of
engine turbocharger as an air source is not allowed. This compressor
eliminates the need for an externally mounted inlet check valve (ICV)
on the air inlet side of the compressor (See Figure 6, page 3).
Refer to Figure 2 below to see the visual differences between the
two BA-921
® compressor heads. Other differences between the two
versions will be referenced throughout this Service Data sheet.
(STANDARD VERSION SHOWN)